Diecasting apparatus

ABSTRACT

The subject invention relates to a novel shot cylinder-gooseneck assembly for diecasting pump wherein a vent passage is formed in the gooseneck wall so as to communicate between the discharge passage of the pump and the space between the shot cylinder and gooseneck wall in which the shot cylinder is mounted. A further improvement consists in the addition of a gasket at the base of the above-mentioned space for sealing off the lower end thereof from the gooseneck passage.

United States Patent [72] Inventor Crescenm F. Fulgenzi Penna, Ohio [21]Appl. No. 835,010 [22] Filed June 20, 1969 [45] Patented June 22, 1971[73] Assignee Union Carbide Corporation New York, N.Y.

[54] DIECASTING APPARATUS 5 Claims, 2 Drawing Figs.

[52) US. Cl. 164/316, 164/410 [51] Int. Cl 822d 17/04 [50] FieldoiSearcb 164/312, 314,316,318;92/165, l71;417/490; 222/385; 18/DIG. 62

[56] References Cited UNITED STATES PATENTS 2,390,263 12/1945 Mills164/316 3,209,418 10/1965 Smith 164/318 3,319,702 5/1967 Hartwig 164/3163,467,171 9/1969 Fulgenzi 164/316 Primary Examiner-J. Spencer OverholserAssistant Examiner-Norman E. Lehrer Attomeys-Paul A. Rose and Robert C.Cummings ABSTRACT: The subject invention relates to a novel shotcylinder-gooseneck assembly for diecasting pump wherein a vent passageis formed in the gooseneck wall so as to communicate between thedischarge passage of the pump and the space between the shot cylinderand gooseneck wall in which the shot cylinder is mounted. A furtherimprovement consists in the addition of a gasket at the base of theabove-mentioned space for sealing ofi the lower end thereof from thegooseneck passage.

PATENTEHJUHZEIQH 3586;095

1%2. I I INVENTOR CRESCENZO F. FULGENZI ATTORNEY DIECASTING APPARATUSThis invention relates to hot chamber diecasting of molten metals andparticularly to an improved novel shot cylindergooseneck assembly for ahot chamber molten metal diecasting pump.

The apparatus of the invention is particularly well suited for use inthe diecasting of high melting point metals such as aluminum andmagnesium. While the diecasting of low melting point metals such aslead, tin and zinc has been in commercial use for many years, it is onlyrecently, since the advent of the hot chamber diecasting system, thatthe diecasting of the higher melting point metals has becomecommercially practical. The present invention is directed to a majorimprovement in this area of use in that it enables the pump service lifeto be greatly extended over prior art hot chamber diecasting systems, asexemplified for example in U. 8. Pat. No. 3,319,702.

In applicant's copending application, Ser. No. 582,848, now U. S. Pat.No. 3,469,621 a diecasting apparatus suitable for use with high meltingpoint metals is described. Briefly, the apparatus described thereinincludes a piston actuated apparatus having a shot cylinder-gooseneckassembly for diecasting molten metal into a die cavity. The assemblycomprises a substantially U-shaped gooseneck having a continuous passagetherethrough. The passage has an inlet end and a discharge end, thedischarge end being adapted to be connected in communication with thedie cavity. The inlet end has a protrusion extending from the innersurface thereof so as to engage a hollow shot cylinder. The hollow shotcylinder extends from the protrusion into the opening in the gooseneckso as to define a void space therebetween. The void space preferably hasa radial dimension of 0.05-inch minimum. The purpose of the void spaceis to permit molten metal to enter the same so as to transmit the forcesresulting from each pressurized shot of metal discharged through theshot cylinder to the outer wall surface thereof. This practice has beenfound to result in a substantial decrease in shot cylinder breakage. itshould be noted that many shot cylinders are formed of materials such astitanium diboride which are very resistant to high-temperaturecorrosion. A difficulty with this material, however, is that it isextremely brittle and hence tends to break in service under normaloperating conditions wherein sudden high-pressure surges of hot metalare inherent in the diecasting process. Often, these surges are of suchmagnitude as to exceed the strength of the shot cylinder. By forming aspace for the metal to enter adjacent the outside wall surface of theshot cylinder, however, a substantial portion of the pressure surges canbe made to act upon both the inner and outer surfaces simultaneouslythus tending to equalize same.

While the use of a gooseneck-shot cylinder assembly employing a voidspace as above mentioned is a definite improvement from a service lifestandpoint, it is still not entirely satisfactory. It has been foundthat although the shot cylinder will no longer break easily in service,the incidence of gooseneck failure due to erosion at a point adjacentthe protrusion is increased.

it is believed that the erosion of the gooseneck areas adjacent the shotcylinder can be reduced by sizing the shot cylinder and gooseneck sothat the space therebetween is very small, e.g., that space which wouldbe inherent in a machinists free-fit. When this space is decreased,however, so as to be less than about 0.05-inch radial, the rate of shotcylinder failure due to breaking from pressure surges tends to increasemarkedly.

It is accordingly an object of the invention to provide a shotcylinder-gooseneck assembly affording greatly increased service life ascompared with prior art assemblies.

Another object is to provide a shot cylinder-gooseneck assembly whereinthe shot cylinder is substantially unaffected by pressure surges ofmetal and wherein the gooseneck will not be prone to failure by erosion.

Yet another object is to provide a shot cylinder-gooseneck assemblyhaving a space formed between the gooseneck wall and the shot cylinderwall but wherein the width of the space is not critical.

In the drawing:

FIG. 1 is an elevational sectional view of a conventional diecastingapparatus embodying the present invention;

FIG. 2 is an enlarged sectional view of the shot cylindergooseneckassembly shown in FIG. 1.

In accordance with applicants invention, in a shot cylindergooseneckassembly for a diecasting pump, a vent passage is formed in thegooseneck wall in which the shot cylinder is mounted so as tocommunicate between the space formed therebetween and the dischargepassage of the gooseneck. The vent passage extends through the gooseneckwall with its lower end terminating adjacent the space between the shotcylinder and gooseneck wall and with its upper end located above thehighest point in such space. Preferably, the lower end of the space isat least partially sealed off by a gasket. The function of the gasketwill be explained fu'rther hereinafter.

Referring now to the drawing, and particularly to FIG. 1, a conventionalpiston actuated apparatus of the hot chamber type for diecasting amolten metal into a die cavity is shown. Essentially, the apparatusconsists of a holding furnace 10 which supports and maintains a meltingbasin or pot 12 which contains the molten metal 13 to be die-cast. Asubstantially U- shaped gooseneck 14 having a continuous passage 15extending therethrough is suspended within the pot 12. The gooseneckpassage 15 has an inlet end 17 and a discharge end 27. The discharge end27 of the gooseneck is adapted to be connected in communication with adie cavity 16. The die cavity is conventional in design and thus is notshown or described in detail. The inner wall of the gooseneck 14 isprovided with a circumferential protrusion 18 adjacent the inner end 17thereof, the same being notched at 19 so as to be adapted to receive andhold a hollow shot cylinder 20 which engages the protrusion via flange23. ln mounted position as shown in the drawing, the shot cylinder 20thus extends from the protrusion 18 into the opening in the gooseneck soas to define a space V therebetween. A pump assembly 30 is positionedinside the gooseneck 14 and on top of the shot cylinder 20. The pumpassembly comprises a housing 22 and a piston 24 adapted to move withinthe bore 21 of shot cylinder 20. The means for actuating the piston arewell known in the art and will not be described. The bore 21 is furtherprovided with a fill port 25 for allowing molten metal to fill the shotcylindergooseneck assembly without requiring the piston to be completelywithdrawn from the shot cylinder.

In accordance with the invention, vent passage means 28 is provided incommunication between the space V and the discharge end 27 of thegooseneck passage 15. The vent passage means preferably extends from aposition in the space V which is closely adjacent the underside of theprotrusion 18 to a position in the passage 15 which is located above thehighest point in space V. In this manner, entrapped gases which mayaccumulate in the space V during each stroke of the piston 24 arequickly vented therefrom. This results in a substantial lessening oferosion at the shot cylinder-gooseneck interface. It has also been foundthat by providing the vent means 28, that the width of space V can bereduced to that which would be inherent in a normal machinistsfree-fit," and still maintain acceptable shot cylinder service life. Itis preferable, however, that the space V be fon'ned so as to be aminimum of 0.05-inch radial as shown in FIG. 2 as distance D. The ventmeans 28 may be formed in the gooseneck wall as a drilled hole, a castport or a lined hole. Preferably, the same comprises a cast in placehollow graphite tube. Each has been used successfully in carrying outthe invention. ln practice of the invention under commercial productionconditions a vent passage having a %-inch diameter has been found wellsuited. The use of the vent passage means 28 has enabled a moltenaluminum diecasting pump to operate without failure to a level of about50,000 cycles, which is considered by many skilled in the art to be theminimum required to consider the process commercially practical.

Another improvement embodied in the present invention consists in theaddition of a gasket 32 disposed between the gooseneck and the shotcylinder at the lower portion of space V, for at least partially sealingoff the lower end of space V from the continuous passage 15. The gasketis preferably formed of expanded graphite material such as Grafoil (aregistered trademark of Union Carbide Corp.) in order to withstand thehigh-temperature corrosive conditions normally encountered in service.The purpose of gasket 32 is to stop or at least retard molten metal fromflowing upwardly from its point of discharge from the shot cylinder intothe space V. Instead, the desired transmission of pressure to the outerwall of the shot cylinder as previously discussed is accomplished viathe vent passage means 20. In this manner the space V can be made to actas a holding zone for molten metal and pressure transmission can beaccomplished as in a hydraulic system with little or no molten metalflow in the space V. This embodiment has been found to still furtherlessen the erosion condition heretofore described. As a result of theuse of this embodiment in combination with the vent passage means 28, itis believed possible to extend the service life of the apparatus toabout 100,000 cycles or more.

While the invention has been described in connection with the specificsystem shown in the drawing it should be understood that many changescan be made to the system without departing from the spirit and scope ofthe invention as defined by the following claims.

What I claim is:

ll. In a shot cylinder-gooseneck assembly for use in a piston actuatedapparatus for diecasting a molten metal into a die cavity andcomprising:

a. a substantially U-shaped gooseneck having a continuous gooseneckpassage therethrough, said gooseneck passage having an inlet end and adischarge end, said discharge end being adapted to be connected incommunication with the die cavity, said inlet end having a protrusionextending from the inner surface thereof;

b. a hollow shot cylinder engaging said protrusion and extendingtherefrom into the opening in the gooseneck so as to define a spacetherebetween,

the improvement comprising vent passage means communicating between thespace and the discharge end of said gooseneck passage for ventingentrapped gases accumu' lated in said space.

2. The improvement in a shot cylinder-gooseneck assembly as claimed inclaim 1 wherein said vent passage means extends from a position in saidspace closely adjacent the underside of said protrusion to a position insaid gooseneck passage located above the highest point in said space.

3. The improvement claimed in claim 2 further including a gasketdisposed between the gooseneck and the shot cylinder for at leastpartially sealing off the lower end of the space from the gooseneckpassage.

4. The improvement claimed in claim 3 wherein said gasket is formed ofexpanded graphite material.

5. The improvement claimed in claim 1 wherein the vent passage meanscomprises a cast in place hollow graphite tube.

1. In a shot cylinder-gooseneck assembly for use in a piston actuatedapparatus for diecasting a molten metal into a die cavity andcomprising: a. a substantially U-shaped gooseneck having a continuousgooseneck passage therethrough, said gooseneck passage having an inletend and a discharge end, said discharge end being adapted to beconnected in communication with the die cavity, said inlet end having aprotrusion extending from the inner surface thereof; b. a hollow shotcylinder engaging said protrusion and extending therefrom into theopening in the gooseneck so as to define a space therebetween, theimprovement comprising vent passage means communicating between thespace and the discharge end of said gooseneck passage for ventingentrapped gases accumulated in said space.
 2. The improvement in a shotcylinder-gooseneck assembly as claimed in claim 1 wherein said ventpassage means extends from a position in said space closely adjacent theunderside of said protrusion to a position in said gooseneck passagelocated above the highest point in said space.
 3. The improvementclaimed in claim 2 further including a gasket disposed between thegooseneck and the shot cylinder for at least partially sealing off thelower end of the space from the gooseneck passage.
 4. The improvementclaimed in claim 3 wherein said gasket is formed of expanded graphitematerial.
 5. The improvement claimed in claim 1 wherein the vent passagemeans comprises a cast in place hollow graphite tube.